Silt grounded King Island cargo ship: ATSB

The hour-long grounding of a cargo ship in harbour at Tasmania's King Island could have been caused by a build up of silt, an investigation has found.

On October 30 the Searoad Mersey reached the island's Grassy Harbour from Melbourne and spent several hours unloading before grounding on the sandy bottom inside the inner breakwater as she tried to depart, causing minor damage and unable to dislodge even with the use of both engines.

"It is likely that the reduction in water depth to the charted depths were the result of the predominant westerly winds blowing sand from the nearby beach into the channel together with the movement of sand within the harbour," an Australian Transport Safety Bureau report released on Tuesday said.